It is estimated that the number of people afflicted with diabetes will increase by 46% worldwide from 2000 to 2010. There are many long-term complications, the most significant being cardiovascular, retinal, renal and neuropathic. The control of blood glucose levels, which currently entails frequent blood sampling, significantly delays occurrence of these complications, resulting in improved quality of life and reduced burden on the health care system. Conventional blood sampling methods are painful and have other undesirable features. Non-invasive (“transcutaneous”) blood sampling methods are an attractive alternative for monitoring glucose, as well as other blood analytes. Of the in vivo measurements reported for a variety of non-invasive techniques, none has demonstrated sufficient accuracy for non adjunctive clinical use. In addition, there has been no substantial verification that the measured signals result from the actual glucose concentrations. Instead, it has been shown that the calibration models derived easily become over-determined, and that chance correlations are picked up as variations in glucose concentrations. This indicates the need for a non-invasive method providing greater specificity.